Brown marsh plaguing Indian River bay

Natural phenomenon affected 100,000 acres in Louisiana

Jonathan Starkey
Staff Reporter

While surveying marshes on the Indian River Bay last month, Chris Bason, a scientist with the Center for the Inland Bays, detected a problem called “brown marsh” or “marsh die-off” that has previously plagued wetlands in parts of the South and Northeast.

For a still unknown reason, parts of the marshes in the Piney Neck area near Dagsboro, which usually thrive with vegetation in the late summer and early fall, had died and turned brown.

“We didn’t know what to think about it,” Bason said late last week. “There was hardly any growth from this year. We don’t know for sure what it is or what is causing it.”

Bason said that some marshes that are usually completely covered with lush vegetation in this time of the year showed only 6 to 25 percent coverage.

After flying over the damaged areas on Friday, Bason and Delaware Department of Natural Resources and Environmental Control (DNREC) officials noticed that the problem was not contained to the Piney Neck area. The “brown marsh,” which can turn vegetated salt marshes into mud flats, has affected patches of marsh throughout the Indian River Bay, officials said.

“We can’t identify one source of the cause,” said Amy Jacobs, an official with DNREC’s Wetland Monitoring Program. “We’re just trying to asses the impact of it, how much area has been impacted and then look into some potential causes.”

Bason, Jacobs and an official with the Louisiana Department of Natural Resources, who is intimately familiar with the phenomenon, said that drought is one primary cause of “brown marsh.”

A fungus or small parasites living within the wetlands can also cause the problem, which affected more than 100,000 acres in Louisiana in the late 1990’s and early 2000’s.

Greg Grandy, a project manager with the Louisiana department, said that his state’s problem was mainly caused by severe drought in the late 1990’s. Snails and other animals living within the marsh then expanded the damaged areas by feeding on the vegetation that had survived, he said.

Although 85 percent to 90 percent of the “brown marsh” cleared when weather patterns again promoted growth in the marshes, Grandy said that some recovery techniques that Louisiana officials used in targeted areas were successful.

One technique involved studying the vegetation that had survived and planting it in other areas. Although that test proved successful on 30- to 40-acre plots, Grandy said, most of the vegetation returned only when the drought ended.

“We had seen it on a much smaller scale. But on this large a scale, we had never seen it to that extent,” Grandy said of the Louisiana outbreak. “The scope and the magnitude is what surprised people,” he added.

“Brown marsh” has not affected Delaware marshes nearly to the extent it did with the drought in Louisiana, but the relatively small amount of die-off could cause large ecological problems.

Delaware’s salt marshes serve as habitats for blue crabs, and certain bird and waterfowl populations that do not nest anywhere else, Bason said. The marshes also serve as a buffer between the water and land when Delaware’s Inland Bays flood. They protect the upland and, many times, residential and commercial property from the flood waters.

DNREC and CIB officials are currently surveying the lands around the damaged area to determine the geographical and ecological impact of the “brown marsh” but don’t yet have any solutions for the new problem on Delaware’s watershed.

“There are so many different things about salt marshes that are important,” Bason said, “So, when something like this happens, you want to find out what is happening and determine possible solutions.”

But, as Bason noted, it’s not that simple. “Because we’re not exactly sure what is causing it, we don’t know exactly how to address the problem,” he said.